Electric wave transmission



Jul 24, 1928. 8 1,678,188

R' C. MATHES ELECTRIC WAVE TRANSMISSION Filed Sept. 1, 1925 5 SheecJs-Sheet 1 4 7 POLARIZ 1R BPF lnveman RoberfCfi/afhea by A/fy July 24, 1928. 1,678,188

R. C. MATHES ELECTRIC WAVE TRANSMISSION Filed Sept. 1, 1925 5 Sheets-Sheet 2 BPF 46/ poumzso //7 vemar: Robe/f6. Maf/vea I m. My

R. C. MATHES ELECTRIC WAVE TRANSMISSION Filed Sept. 1, 1925 5 Sheets-Sheet 3 PoLAmz wommzzo A A/fy July 24, 1928. 1,678,188

R. c. MATHES ELECTRIC WAVE TRANSMISSION Filed Sept. 1, 1925 5 Sheets-Sheet 5 POLARIZED 7 7 AR 2 POLRRIZ OLARIZED Patented duly 24, 1928.

UNITED STATES PATENT OFFICE.

ROBERT C. MATHES, 0F WYOMING, JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y A CORPORATION OI NEW YORK.

ELECTRIC WAVE TRANSMISSION.

Application filed September 1, 1925. Serial m. 53,777.

This invention relates to electric wave transmission, for instance over circuits having distributed therealong a plurality of so called voice operated or voice pointed repeater sets or other translating devices, and aims to efficiently control such-devices n a prearranged" manner from dilferentpomts, such as the opposite ends of the circuits, and to improve the operation of voice operated repeater sets and systems employing them,

especially with regard to avoiding confusion in case two talkers at opposite ends of a circuit having such sets in tandem therein start talking at nearly the same time.

-A voice operated repeater set transm1ts voice currents or like transmission efficiently in onlv one direction at a time, and is controlled by the transmission to insure that the set is con itioned for efliciently repeat ng in the proper direction, in order to provide for two way repeating. The system specifically described hereinafter and shown in the drawing as embodying one form of the present invention has such sets 1n tanden 1 in a circuit, and in order to obtain eflicient through or overall transmission in one direc tion over the circuit the tandem connected sets must all transmit efficiently in that direction at the same time. Consequently the problem arises of determining the control of the circuit when two talkersat its opposite ends start talking at nearly the same. time. The first talker should control the circuit and in accordance with this form of the invention, whichever ones talk reaches the central repeater first is given complete control of the circuit.

To accomplish this operation, thesystem employs an auxiliary control circuit, in addition to the talking circuits, the use of the auxiliary circuit generally being preferable to carrying control current on the talking conductors in the frequency range outside of the essential range of the voice currents or the like. Sources of control current of distinctive frequencies are provided at the terminal repeater stations. The system 15 so arranged that, when voice energy. is introduced into either terminal station for transmission to the other terminal station no attempt being made to transmit in both directions at the same time, a fractionof the voice current energy is employed for (1) causing to each of the through repeater stations, 10-

cated between the terminal repeaters, to condition the, through repeaters for efiicient transmission toward the terminal repeater distant from the speaker, and (2) causing the repeater set at the near terminal repeater station to be conditioned for eflicient transmission toward the distant terminal station. The voice current energy which is to be transmitted to the distant station is passed through a transmission delay circuit or path in the near terminal repeater set before being transmitted from the set, the delay thus introduced "in the transmission. of this part of the ,voice current energy not only facilitating the operation just mentioned of conditioning the near terminal repeater for efficient transmission without loss of transmission due to the time required for such conditioning but further, resulting in the control energy sent along the control circuit arrivingat each of the repeater stationswhich it is'to control, before the speech energy, circuits of equal grade or speed'preferablybeing used for transmittin the speech current and the control impu ses between stations since the delay obtained by the delay circuit avoids any necessity for employing higher propagation speed for the control energy than forthe speech energy, between the stations. The delay introduced by the delay circuit is made such that the first syllable, in traversing the talking conductors, will be thus preceded at each through repeater station by the'control current on the control circuit, by a time suflicient for the control current to condition the repeater first to arrive at the center repeater station will operate equipment at that point which will prevent the other control frequency from passing that repeater and thus from reversing the pointing of the repeater sets already pointed by the first frequency. This first frequency will, however, proceed beyond the center repeater and reset any repeaters there which may have been set'by the second frequency.

Other features and objects of the invention will appear from the following description of the invention taken in connection with the accompanying drawings, wherein Figs. 1 to 5, placed side by side in numerical order from left to right, show a system-embodying a form of the invention.

In that system, a control line 1, for transmitting the control currents referred to above, is made to serve a number of talking circuits by the assignment of control frequencies, two for each talking circuit, the circuits for transmitting the control currents being generally similar to the carrier current circuits in the well known grouped frequency system of carrier current telegraphy.

Three talking lines or circuits are shown, designated 2, 3, and 4 respectively, and placed on the drawing one above theother in numerical order from the bottom of the drawing up, line 2 with its repeater sets R, to R being shown below the dash line 5'5, line 3 with itsrepeater sets R to R being shown between the dash line 5-5 and the dash line 6-6, line 4 with its repeater sets R to R being shown between the dash line 66 and the dash line 7 7 and the control line 1, with repeater sets R}, to R for repeating the control currents, being shown above the dash line 77. Each one of the systems is shown as having five repeater stations, one constituting each figure of the drawing. The stations constituting Figs. 1 and 5 are terminal stations and will be referred to as the west terminal station and east terminal station, respectively; the station constituting Fig. 3 is the center repeater station, and the stations constituting Figs. 2 and 4 will be referred to as intermediate repeater stations, being located intermediate the center station and a terminal station. The twoterminal stations are shown alike, except that they are symmetrically reversed, and except that they are arranged to generate and receive different control frequencies. The two intermediate stations are also shown alike, except that they are symmetrically reversed with respect to each other.

Each of the fiverepeater stations comprises three two-way, voice pointed, telephone 11epeater sets, one set in each talking line; and,

moreover, the center station and the intermediate stations comprise a two-way control current repeater each, in-line 1, for repeating the control currents referred to above. Certain of the telephone repeaters are of the so called biased type and the others are of the so called neutral type. These types are distinguished in that, after a period of trans mission in the repeater circuit, the biased repeater is left in condition to transmit efliciently in the line circuit only in the direction in which it last transmitted, until transmission in the other direction over the circuit is initiated, whereas, after such a period of transmission the neutral repeater will not efficiently transmit in either direction until new transmission takes place condi tioning the circuit to transmit efliciently 1n the line circuit only in the direction of transmission. The circuit of line 2 will be referred to as of the neutral type, since its voice operated repeaters are all of the neutral type. The circuit of line 3 will be referred to as of neutral-biased type, its terminal repeaters being of the neutral type while its other repeaters are of the biased type. The circuit of line 4 will be referred .to as of biased type, since all of its re peaters are of the biased type. It will be understood that ordinarily the repeater stations are considerable distances apart. It will also be understood that although only one intermediate repeater station, or one intermediate repeater set for each of the talking lines, is shown, between the center reeater station and either terminal station, a arger number of the same kind of intermediate repeater sets may be employed, in tandem, in any talking line, between the center station and each terminal station.

Associated with the repeater R, of line 2, at the west terminal repeater station, is a source 12 of control current of frequency f,. A similar source 13, of frequency f,, is associated with the east terminal repeater R of line 2. Likewise, sources 14, 15, 16 and 17, of frequencies i f,, f, and f respectively, are associated with the terimnal repeaters R R R and R respectively. The sources 12, 14 and 16 are connected to west terminal control channel 20 and through that channel to the west end of line 1, band pass filters 21, 22 and 23 for passing frequencies f f and f,, respectively, being connected between the sources 12, 14 and 16, respectively, and the channel 20. The designation BPF, wherever occurring in drawing, indicates a band pass filter. Similarly, the sources 13, 15' and 17 are connected to east terminal control channel 24 and the east end of line 1 through band pass filters 25, 26 and 27 for passing frequencies f f and f respec-. tively. The sources 12 to 17 are normally short-circuited, however, with respect to the filters21 to 23 and 25 to 27 so that in the absence of speech transmission in the system no control impulses are sent over line 1. The band pass filters 21 to 23 and 25 to 27, and also the other band pass filters referred to hereinafter, may be, for example, of the type disclosed in U. S. patent to G. A. Campbell,

1,227,113, May 22,1917.

At the control current repeater set R band pass filters 30 and 31 select for eastwardly pointed amplifier 32 a group of frequencies including f f f and any other control frequencies to be transmitted eastward if such other frequencies are present in line 1 by reason of line 1 being employed to control talking lines, not shown, other than 2, 3 and 4. Similarly, at repeater set R band filters 33 and 34 select for westwardly pointed amplifier 35 a group of frequencies including f f f and any other control frequencies to be transmitted westward over line 1. Thus, these four filters are grouping filters for accomplishing frequency separation of the eastwardly directed grou of control frequencies from the westward y directed, group. 'At the repeater set R there are also means, for instance, tuned loops 36 to 43, for suppressing, each control frequency in the Westwardly directed group of such frequencies, each of the tuned loops suppressing one of those frequencies. However, short circuits for the tuned loops are provided through the back contacts of relays F, 127 and I at the repeaters R R and R respectively, so that in order for one of these tuned loops to be effective to suppress a control frequency it is necessary that the corresponding relay be operated to remove the short circuit from that loop.

At the control current repeater set R band pass filters and 46 select for amplifier 47 the group of frequencies passed by filters 30 and 31 of repeater set R and band filters 49 and 48 select for am lifier 50 the group of frequencies which lters 33 and 34 at repeater set R pass. At the repeater set R there are also tuned loops 56 to 63 which correspond in structure and function to the loops 36 to 53, respectively at repeater set R Moreover, at the repeater set R are also similar loops 66 to 73, for suppressing each control fre uency in the east- ,wardly directed group 0 such frequencies,

' each loop suppressing one frequency. Short circuits for the loops 66 to 73, as w'ellas short circuits for the loops 56 to 63, are provided, through the back contacts of relays F, 132 and 133, and I, at the repeaters R R and R respectively, so that in order for one of these tuned loops to be effective to suppress a control frequency it is necessary that the corresponding relay be operated to remove the short circuit from that loop.

a At the control current repeater set R are band pass filters 75, 76, 77 and 78 for accomplishing frequency separation of the control frequencies to be amplified by eastwardly pointed amplifier 79 from those to be amplified by the Westwardly pointed amplifier-80, and also tuned loops 86 to 93,

hand filters 94, and 96 for selecting the frequencies f,, f,, and f,, respectively, and transmitting them to amplifier-rectifiers 97, 98 and 99, respectively, for controlling relays as described hereinafter. rectifiers and also the others referred to herein,'may be, for instance, of the type disclosed in U. S. patent to E. D. Johnson 1,526,550, Febr'uary'17, 1925 or of the type disclosed in my application Serial No. 667,437, filed October. 9, 1923, entitled Electric current transmission. i

At the west terminal repeater station are band pass filters 101, 102,an'd 103 for selecting the frequencies f f and f respectively, and transmitting them to amplifier-rectifiers 104, 105 and 106, respectively, for controllin relays as described hereinafter.

At the repeater setR is a receiving set to select from the frequencies transmitted through the amplifier 32 the frequency f,, for controlling relays A2, B2 and E at the repeater set R,. The designation Rf or Rf etc., herever occurring in the draw-' ing, indicates a receiving set for frequency f, or f etc. This receiving set should include a selective circuit, such as a series tuned circuit (not shown) resonant to f, or a band pass filter (not shown) for passing f,, and an amplifier-rectifier (not shown for converting the control of frequenc 7 into direct current for operating the re ays 'A2, B2 and E. Also at the repeater set R is a receiving set 111 to select from the frequencies transmitted through the amplifier 35 the frequency f,, for controlling relays C2, D2 and F at repeater set R,,. This receieving set, and also the others referred to hereinafter, may be like the receiving set 110, except that the frequency selected is not the same in all cases. f p

At the repeater set R, is areceiving set 115 to select from the frequencies transmitted through the amplifier 47 the frequency f,, for controlling relays A3,- B3 and one of the F relays at the repeater set R This receiving set is likethereceivin set 110 just described. At the repeater set a is also a receiving set 116, to select from the frequencies transmitted through the vamplifier 50 the frequency f,, for controlling relays C3, D3 and the other F relay at the repeater set R,. This receiving set is like the receiving set 111.

At the repeater set R, is a receiving set to select from the frequencies transmitted through the amplifier 79 theirequency f for controlling relays A4, B4 and F at the repeater R this receiving set being like the receiving set 110. At the repeater set R, is also a receiving set 121, to select from the These amplifierfrequencies transmitted through the amplifier 80 the frequency f for controlling re lays C4, D4 and E at the repeater set R this receiving set being like the receiving set 111.

At the repeater set R is a receiving set 125 to select from the frequencies transmitted through the amplifier 32 the frequency f for controlling relay G, at the repeater set R,; and at this repeater is also a receiving set 126 for selecting. from the frequencies transmitted through the amplifier 35 the frequency A. for controlling relays H and 127 at this repeater set.

Similarly, at the repeater set R,,, receiving set 130 selects frequency 7, to control relays G2 and 132; and receiving set 131 selects frequency ,flto control relays H2 and 133.

Similarly, at repeater set R,,, receiving set 135 selects frequency f, to control relays G3 and 137; and receiving set 136 selects frequency f, to control relay H3.

At the repeater set R receiving sets 140 and 141 select frequencies f, and f respectively, to control relays as described hereinafter. Similarly, at repeater, set R receiving sets 142 and 143 select frequencies f and f respectively, and at repeater set R receiving sets 144 and 145 select frequencies f, and f respectively, to control relays as described hereinafter.

Subscribers telephone sets 150,151 and 152 connect with the repeater sets R R and R respectively, by means of hybrid coils or balanced three-winding transformers 153, 154 and 155, respectively, and impedance balancing networks 156, 157 and 158, respectively; and similarly, subscribers telephone sets 160, 161 and 162.c0nnect with the repeater sets R,,, R and 'R,,,, respectively, through hybrid coils 163, 164 and 165, respectively, and impedance balancing networks 166, 167 and 168, respectively. However, the balance between the networks and their associated subscribers loops may be only nominal.

The connection of the repeater sets R R and R to the lines 2, 3 and 4, respectively, is by means of hybrid coils 170, 171 and 172, respectively, and balancing networks 173, 174 and 175, respectively; and the connection of the repeater sets R R and R to the lines 2, 3 and 4, respectively, is by means of hybrid coils 180,181 and 182, respectively. and balancing networks 183, 184 and 185, respectively; but the balance between the networks and their associated toll lines may be only nominal.

Before describing the operation of the circuits of the system which involve tandem operation of repeater sets, the operation of individual repeater sets of the types involved will be described.

Considering the terminal, neutral type repeater set R speech energy from the subscribers set 150 enters at the toll line terminals and passes to the input of eastwardly ointed repeater amplifier 200 by way of the bridge terminals of the hybrid coil 153. After amplification by amplifier 200, part of this energy is transmitted through a delay circuit or path 202 and the hybrid coil 170, to the line 2, but a portion is taken by amplifier-rectifier 201 and operates relays A1 and. B1. The designations DP and AR, wherever occurring on the drawing, indicate a delay path and an amplifier-rectifier, respectively. The delay circuit or path 202 may be of any type suitable for producing the desired delay in the propagation of signals therethrough. The relay A1 opens a short circuit on the output of the delay circuit or path 202 for a sufl'icient interval and at the proper time to permit the transmission of each syllable of speech to the line 2 as it emerges from the delay circuit. The operation of relay B1, by opening a short circuit on the generator 12 of frequency f,, results in the transmission out upon the control line 1 of control impulses corresponding to each syllable of transmitted speech. The

time of operation of this relay is so related to the time of lag introduced by the delay circuit that this control impulse precedes spee'ch in reaching each of the repeater stations to the east of repeater set R, by a time sufiicient for cutting the repeater in at that station. This time relation is maintained all along the circuit so that each syllable finds each successive repeater cut in for it at the proper time. Preferably the delay time of the delay circuit is so related to the switching time of the relays that none of any syllable will be lost.

In the operation of this terminal repeater set R on receiving speech energy delivered from the line 2 the hybrid coil 170 and control current of frequency f which is delivered from the line 1 through the filter 101 and the amplifier-rectifier 104, relays C1 and D1 are operated by the control impulses, which are sent out preceding each syllable from the distant terminal station. There is, therefore no delay circuit required in the receiving branch of the circuit of the repeater set, relay D]. opening in time to permit the passage of the received speech amplified by Westwardly pointed repeater-amplifier 203, While relay C1 functions to prevent the operation of the relays A1 and B1.

In order to allow for transient reflection of received speech energy from the connected circuit 150, the contact shown as part of relay Cl should be arranged to be slow closing, for instance, by the use of a slow operated relay of the ordinary type or any suitable type as relay C1, or else the closing of the circuit extending through the contact should be delayed after those contacts close, for instance in the manner in which the closing scribed hereinafter.

-D10 correspond to the relay B1 of set R their relays A5, C6 and A10 corres 0nd to the relay C1 of set R and their re ays B5, D6 and B10 correspond to the relay D1 of set R,. The westwardly pointed repeater amplifier 210 or repeater set R the east- Wardly pointed repeater amplifier 300 of set R5, and the westwardly'pointed amplifier 3100f repeater set R correspond to the eastwardly pointed repeater amplifier 200 of the sending branch of set R the amplifierrectifiers 211, 301 and 311 of repeater sets R R and R 5, respectively, correspond to the amplifier-rectifier 201 in the sending branch of repeater set R,; the delay circuits 212, 302 and 312 of repeater sets R R and R respectively, correspond to the delay circuits of repeater set R and the repeater amplifiers 213, 303 and 313 in the receiving branches of repeater sets R R and R respectively, correspond to the repeater amplifierR203 in the receiving branch of repeater set Considering, now the operation of the ina tel-mediate neutral type repeater set R and assuming speech energy to be approaching the set over line 2 from the. west, an impulse of frequency f, which just precedes it and reaches the repeater set R, over the control line 1 is amplified by the control circuit amplifier 32, selected by the receiving set 110, and operates relays A2 and B2. The opening of the contacts of these relays arranges the connections of the sin le repeater amplifier 205 in the line 2 so t at the amplifier will amplify from west to east in the line. At the end of the control impulse the repeater is again rendered inoperative to amplify in either direction in the line. Similarly, for speech in the direction from east to west, a control impulse of frequencyv 2 opens the contacts C and D rendering t'e same telephone repeater amplifier 205 operative to amplify from east to west in the line 2. Thus, the repeater set is normally in a neutral condition, waiting to be rendered operatiye to repeat in either direction, only one direction at a time, uponreceiving a suitable control impulse for each syllable. The functions of relays E and F will be de- The repeater set R, is like the set H, except that the relays E and F are operated by frequencies f, and f instead of by f, and f respectively. The operation of R will be apparent from the description of the opera tion of R and the description given hereinafter of the operation of line 2 as a whole, Repeater 209 corresponds to repeater 205 of set R. and relays A B. C 1),, E and F correspond to relays A B C 1),, E and F, respectively, of repeater set R,.

The repeater set R, is like the set R,,, except that R has two F relays and no E relay. The operation of R will be apparent from the description of the operation of R and the description given hereinafter of the operation of line 2 as a whole. Repeater 207 corresponds to repeater 205 of set R and relays A B C and D and F correspond to relays A B C ,D and F, respectively, of the repeater set R Considering now, the type of biased repeater set employed in line '3 at the center and intermediate repeater stations, repeater set R comprises a single repeater amplifier 320, polarized switching relays 321 and 322 for reversin the pointing of re eater 320 in the circuit 3, control relays 1 and H1 responsive to control frequencies f, and f respectively, to control the switching relays, and relay 127 responsive to f, for a purpose which will be madeapparent hereinafter. When an impulse f which should condition the repeater for amplifying from west to east in the circuit 3, energizes relay G1, the circuit through the left hand windings of relays 321 and 322 is opened, and the current flowing in the right hand windings through the contact of relay H1 throws the armatures of relays 321 and 322 to the positions shown, so that repeater 320 will amplify from west to east in line 3; When the control impulse ceases and the contact of relay G1 closes, the current in the left hand windings of relays 321 and 322 annuls the effect of the current in the right hand windings, but the armatures remain in the positions shown through the natural bias of the relays 321 and 322. They will remain in that position during and between all succeedin as an lmpulse of frequency f is received at the repeater set R however, the contact of relay H1 is opened, and consequently the armatures of relays 321 and 322 are thrown to their other contacts, so that the repeater is conditioned to amplify from east to west in the line 3. It will remain in that condition until speech is again sent from the west toward the repeater. If desired, relays G1 and H1 may be so called vibrating relays, for instance, of the type disclosed in U. S. patent to S. G. Brown, 1,185,472, May 30, 1916, or U. S. patent to Ericsson and Dahlstrom, 1,169,387, January 25, 1916.

Repeater sets R and R are like set R except as regards relays 132 of set R, and relay 137 of set R,. The function ofthese relays will be developed later. The eleimpulses of frequency f As soon ments 330, 331, 332, G2 and H2 of set R,, and the elements 340, 341, 342, G3 and H3 of set R,,, correspond respectively to elements 330, 331, 332, G1 and H1 of set R,.

Considering now, the type of biased repeater set employed in line 4, the repeater set R,,, for instance, has a single repeater amplifier 401, with a connection to its input side from the bridge points of the hybrid coil 155 by means of a hybrid coil 402 and balancing network 403, a connection to its input side from the bridge points of the hybrid coil 172 by means of the hybrid coil 402 and balancing network 403, a connec-.

tion from its output side to the series winding of the hybrid coil 155 by means of a hybrid coil 404 and balancing network 405, and a connection from its out ut side to the series winding of the hybri coil 172 by means of the hybrid coil 404 and balancing network 405. The first of these connections includes a delay circuit 406 and may be short-circuited by the contact of a relay A,,

or opened by means of the contact of a relay F,. The second of the four connections may be short-circuited by the contact of a relay 0,, or opened by means of the contact of a relay G,. The third connection may be short-circuited by means of the contact of a relay D,, or opened by the contact of a relay H,. The fourth connection may be short-circuited by means of the contact of a relay B,,"or opened by means of the contact of a relay 13,. When the first and fourth connections are effective, the repeater is pointed east; and when the second and third connections are effective, the repeater is in condition to amplify from the line 4 to the subscribers loop 152. An amplifierrectifier 407 controls certain of the relays mentioned, in a manner which will be made apparent hereinafter; and relays J and K, are provided for control purposes made apparent hereinafter. Relays A1, B1, C1 and D1 are polarized, so that in the absence of any energizing current the armature of each relay remains as operated by one of the windings of that relay until the other winding of that relay is energized. The direction in which each Winding when energized tends to actuate an armature is indicated by an arrow on the drawing.

The other terminal repeater set for line 4, designated R is similar to the set R,,, relays (3,, G,, F, and A of set R corresponding to the relays A,, F,, G,, and (1,, respectively, of set R,,, relays B E H and D of set R corresponding to the relays 1),, H,, E, and B,, respectively, ofset R,,, repeater441, hybrid coils 442 and 444 and networks 443 and 445 of set R, corresponding to the repeater 401, coils 402 and 404 and networks 403 and 405 of set R,,, delay circuit 446 and amplifier rectifier 447 of set R, corresponding to delay circuit 406 and amplidesignated A, B, C, D, E, F, G and H relays in repeater sets R, to R, as in the case of repeaters R,, and R,,,, but with subscripts 2,

3 and 4, in the case of the repeater sets R R, and R respectively. In these three sets the repeater amplifiers and the hybrid coils and balancing networks permanently connected to those amplifiers are designated the same as the corresponding elements in set R,,, except that the designating number is lncreased by 20 in the caseof each of these elements for repeater sets R,,, by 30 in the case of each of the elements for repeater set R,,, and by 40 in the case of each of these elements for repeater set R Hybrid coils 427 and 429 and balancing networks 428 and 430 of repeater set R, hybrid coils 437 and 439 and balancing networks 438 and 440 of repeater set R,,, and hybrid coils 447 and 449 and balancing networks 448 and 450 of repeater set R,, correspond to the hybrid coils 155 and 172 and balancing networks 158 and 175 of the repeater set R,,. The functions of relay I in set R,,, relays I in set R and relay I, in set R,, will be made apparent hereinafter.

In the operation of the neutral circuit comprising line 2 in transmitting from west to east, speech from the west, from telephone subset 150, will enter repeater set R,, and after amplification by repeater amplifier 200 part of the energy is taken by the amplifierrectifier 201 and operates the relays A, and B,. Relay A, opens a short circuit on the output of the delay circuit 202 to permit the transmission of each syllable of speech as it emerges from the delay circuit. It should be open a sufiicient interval of time to permit the complete transmission of each syllable of speech, and as the time of transmission through the delay circuit is increased its release time should be lengthened to avoid clipping off the tail end of syllables. This lengthening may be accomplished by condenser 204 shown connected to becharged on closing of the relay contact. The opening of relay B, sends a. control impulse from the generator '12 of frequency I), along the control line. As noted above, this control impulse Will precede speech, on account of the time lag introduced by the delay circuit, in reaching each of the repeater stations to the east of repeater set R, by a time suflicient to allow for cutting the repeater in at that station, this time relation being maintained relay contact.

When the control impulse f, reaches the intermediate repeater station R it is amplified by repeater 32 for the control channels and after separation by receiving set 110 operates relays A2, B2 and E. The first two relays cut the repeater 205 in circuit and the last breaks the output of the opposite control rectifier of receiving set 111 to the relays D2 and Q2, but not to the F relay.

The control impulse would continue along the control channel and reaching the center repeater R operate the A and B relays, cutting in the repeater 207, and open the F relay which controls the short circuit on loop 66 tuned to frequency f, and thereby prevents transmission of F 2 through amplifier 50. Therefore, should an. impulse of frequency 7, come from the east after the repeater 207 has been thrown for speech transmission from west to east, it could do nothing. If the repeater R to the east of the center repeater is in neutral position when the control'in'ipulse f arrives it will cut it in by operating relays A4 and B4 and prevent transn'iission of. f through amplifier by opening the F relay which controls a short circuit on loop 86 tuned to frequency f If a control impulse f from the east gets to this station It, before 7, it operates relays D4, ()4 and E, the relays C4 and D4 pointing the repeater 209 east to west, and the relay E interrupting the f, control of the A4 and B4 relays, but not of the F relay; now when 7, comes a moment later it operates the F relay, thereby cutting off the input to the D4, C4 and E relays and causing them to release, and thus permits the A4 and B4 relays to be operated to point repeater 209 from west to east and thus make transmission of speech from west to east possible. It will be noted that the repeaters to the east of the center are under control of f, whether 7, or f reaches them first. The interlocking E relay at repeater set R prevents the A4 and B4 relays from being simultaneously operated with the D4 and C4 relays, which would permit the repeater 209 to sing. The E relay at repeater set R, similarly prevents repeater-205 from singing.

WVhen the control impulse 7, reaches the east terminal station it' operates relays B5 and A5. The opening of the former permits speech transmission to the east through repeater amplifier 213. The opening of the latter stops speech and control energy transmission to the west.

The center repeater has two F relays; so that which ever control frequency gets there first controls the circuit. In the gaps between words coming from the west, part of control impulses f, from the east may get by and reverse repeaters to the west of the center rep-eater R Interference between control impulses, due to such operation, should be guarded against. If the F relay, which stops the transmission of one control frequency be given a relaxation time slightly greater than twice the time of transmission to the next repeater the combined operation of two neighboring stations will cut-off any interference from the control impulse that has been trapped between two stations. This end can also be accomplished by giving relay,

B1 that much additional delay in releasing so that theadditional length of the control impulses will hold any station'operated for a length of time equal to the timeof transmission between stations after the next succeeding station has been properly operated. Condenser 208, shown connected to be charged from the contacts of the F relays may be used to obtain the desired relaxation time for those relays, as the condensers correspondingly-connected to the A1 and B1 relays serve to delay their closing.

After west or telephone set 150, gets through talking the circuit remains locked up against a reply for the time of transmission in one section after his last word reaches east or telephone set 160. East can, therefore, break in only when wests pause in speech is longer than the time of transmission of the circuit plus the time of transmission of one section, which latter time is the relaxation time of the terminal repeater. The operation of this circuit in transmitting from east to west is similar to the operation just described for west to east transmission, and will be apparent without further description.

In the operation of the neutral-biased circuit comprising line 3, which circuit is shown biased from west to east, when west or telephone set 151 talks, it'would operate,

by control impulse f control relay G1 at the first intermediate repeater R The opening of G1 would permit the polarized switching relays 321 and 322 to be thrown into the position shown. At the center repeater R the control impulse f, not only operates the control relay G2 but also prevents the transmission of f, by operating relay 132 which removes a short circuit from loop 67 tuned to frequency F,. f, will repeat the same thing at the repeater station R, to the right of the center station if f, is not present. Now suppose f, reached the repeater R before 7, and by operating relay H3 threw the switching relay ton ues to the right hand contacts, thereby pointing'the repeater from east to west, 7, coming shortly later would by operation of the relay 137 open the short circuit about loop 87 tuned to frequency f and thereby interrupt the transmission of f causing the H3 relay to release; and the operation of the G3 control relay would cause the switching relays 341 and 342 to point the repeater from west to east. The' operation of the circuit for east to west transmission is similar to the reverse operation just described, and will be apparent without further description.

The biased type circuit comprising line 4 is shown biased from west to east. 'This biased circuit is distinguished by being operated by the opening of relay contacts. Considering the operation of the system for speech transmission from east to west, part of the energy coming from the hybrid coil 165 is taken by the am lifier-rectifier 447 and operates relays K D E F A and B The opening of K removes a short circuit from the generator 162 of frequency i and sends a control impulse along the control line 1. E and F should open a little before 0 and D in order to prevent the repeater from singing when the latter two reays are opened. WVhen A and B have been closed there is no necessity that relay contacts E and F, should be open. Therefore E and F should only stay open until the final make of A and B because when E and F are closed the repeater will be operative in the other direction on the opening of relay contacts instead of on the closing of relay contacts. E and F are tem orarily opened by the char ing current of a condenser 460 that is p aced in series with the relay windings; the relay windings and the condenser are shunted by a suitable resistance 461.

Continuing west from the east terminating repeater R, 'the control impulse f,, on reaching the first intermediate repeater R will operate the C D,, E,,, F,, A and B relays, thereby cutting the repeater B in. At the center repeater R it operates the C D E F A and B relays pointing the repeater from east'to west, and also the I, relay, which removes a short circuit from about the loop 58 tuned to frequency f, and thus prevents the transmission of the frequency 7", from the other or east side. If f reaches the repeater R to the left of the center repeater-before f, it will operate the same series of relays as at the center repeater (02, D21 E2) za A27 B2 and But arrives at the repeater R, before f it will Operate the relays H and G (the A B D and C relays are already operated as shown on the drawing). H and G are opened only for the time that it takes D and C to close. Now when i arrives suppose H. and G. have had time to close. f

will interrupt the transmission of f, by operating I to iemove a short circuit from have not had time to close before the other relays are operated beginnings of words might be destroyed if the time delay in the delay circuit were not made long enough. Let us consider the worst possibility. viz, G and H have just been operated when 7', interrupts the transmission of f, by openin 1 f and f, must have met to the right 0' the repeater a distance the impulse traveled during'one-half the time of break of relays H and G The increased switchin time of the repeater would then be equal to the time of make minus half the time of break of the H or G rela s. It f and f, meet just at the repeater 2 and G would not have time to open before f is interrupted by the opening of the I relay. At the receiving terminal repeater f besides pointing the repeater in the right direction breaks the input of the amplifier-restifier supplying the terminal relays for west.

The operation of this circuit in transmitting from west to east is similar to the operation described for transmitting from east to west, and will be apparent without further description.

The center repeater station, comprising the center repeater sets, is prefarably lo coted near the electrical center of the length of the talking circuits, as regards the propagation time required for the speech current energy to be transferred from one end of those circuits to the other end.

What is claimed is:

1. In combination, a plurality of translating devices, apparatus, including current transmission means having said translating devices distributed therealong, for controlling said translating devices over said means from each end of said means, and apparatus controlled over said means from one end of said means for annulling control of certain of said devices which has been obtained through said means from the other end of said means.

2. A system comprising a plurality of repeater sets connected in tandem, means for pointing each set in either direction, and means responsive to transmission forv controlling said first means and giving the transmission in either direction complete control of the pointing of the repeaters even though while transmission in that direction is traversing the circuit transmission in the other direction causes one of the repeaters to be pointed in said otherdirection.

3. In combination, a circuit, repeaters in tandem therein, including terminal repeaters and repeaters between said terminal repeater, means at each of said repeaters for controlling the transmission eificiency of that repeater, means at one of said repeaters between said terminal repeaters for controlling said transmission efficiency controlling means at another of said repeaters between said terminal repeaters, and means responsive to transmission to be repeated by said tandem connected repeaters for controlling said means at said one repeater.

4. In combination, a repeater circuit comprising a plurality of two-way repeater sets connected in tandem, means for conditioning each set for eflicient transmission in only one direction at a time, means responsive to the transmission to be repeated in either direction by said repeaters for controlling said first mentioned means, and means for giving the first started 'oftwo oppositely directed transmissions control over the circuit to the exclusion of control by the second started transmission, when control of said first men tioned means through said second mentioned means has. been partly obtained by said second started transmission before said first started transmission has completed control of said first mentioned means by said second mentioned means.

5. The combination set-forth in claim 4, in which said second mentioned means comprises means for transmitting control energy, in each direction between points at the terminals of said circuit and said means for giving the first started transmission control over the circuit comprises means for causing the controlenergy transmitted more than substantially half way between said points in one direction to annul the controlling action of control energy transmitted in the other direction.

6. The combination set forth in claim 4,

in which said second mentioned means comprises means for transmitting control energy in each direction between oints at the terminals of said circuit an said means for giving the first started transmission control over the circuit comprises means for causing the control energy which reaches the repeater set nearest the center of the circuit first to stop transmission of oppositely directed control energy.

7. A circuit comprising neutral and biased types of two-way repeaters in tandem, each of said repeaters having means for conditioning the repeater for efiicient transmission in only one direction at a time, and means responsive to transmission to be repeated by said repeaters for controlling said first means.

8. A circuit comprising a two-way biased repeater and a two-way neutral repeater in tandem, each of said repeaters having means, controlled by the transmission to be repeated, for conditioning the repeater for efiicient transmissionin only one direction at a time.

9. A circuit comprising two terminal repeater sets of neutral type and another repeater set of biased type in tandem, each of said terminal sets having means for pointing that set in either direction in the circuit, said other set comprising means of different character for pointing said other set in either direction in the circuit, and means responsive to transmission to be repeated by said repeaters for controlling said means for pointing the terminal sets and the other set.

10. An electric wave transmission system comprising a signaling channel extending between two terminal stations and a repeated control channel extending between said stations, said signaling channel comprising terminal repeater sets and other repeater sets in tandem, means at each of said signaling channel repeater sets for pointing the set in either direction in thechannel, and means at each of said terminal stations responsive to the signaling energy at that station for sending control energy from that station over said control channel to each of said pointing means.

11. A system according to claim 10, in which the means at the terminal stations for sending control energy over the control channel employ currents of distinctive frequencies for carrying the control energy over the control channel.

12. A system comprising a signaling channel, a control channel, translating devices in said signaling channel, means at each of said devices for controlling that device, a source of control energy at each'end of said controlchannel, means at each terminal of the signaling channel, responsive to the signals sent from that terminal toward the other terminal for sending control energy from one of said sources over control'channel to said means at said devices, and means for delaying the transmission to each of said devices of signaling energy with respect to the control energy sent in response to that signaling energy.

13. In combination, a circuit, a repeater comprising means responsive to transmission in said circuit to be repeated in one direction for conditioning the repeater for efiicient transmission in that direction, means for delaying the passage of transmission through the repeater in said direction with respect to the passage of said transmission to said transmission responsive means, means for conditioning the repeater for efiicient transmission in said circuit in the opposite direction, and means responsive to said transmission in said circuit in said opposite direction at a point remote from the repeater for controlling the third mentioned means.

14. A signaling system comprising a signaling channel, repeaters connected in tandem in said channel, a control current channel, means for conditioning each of said repeaters for efiicient transmission of signals in one direction only at a time, and means responsive to said signals for controlling said first means over said'control current channel from each end of said signaling channel.

15. A system comprising a signaling chan- Y nel, a separate control channel, translating devices in said signaling channel, means at each of said devices for controlling that device, a source of control energy at each end of said control channel, and means at each terminal 6f the signaling channel, responsive to the signals sent from that terminal toward the other terminal for sending control energy from one of said sources over said control channel to said means at said devices.

16. A system in accordance with claim 15, in which the sources of control energy are of different frequencies.

In witness whereof, I hereunto subscribe my name this 31st day of August, A. D. 1925.

ROBERT C. MATHES. 

